[PSUBS-MAILIST] Speaking of MBT valve
Jon Wallace
jonw at psubs.org
Sat Nov 23 19:31:23 EST 2013
A 600psi valve should be fine on the 350 as long as you keep any static
pressure for the fill side a safety margin below, perhaps no higher than
350psi. A first stage on your hp tank indicates a flowing pressure of
150psi or there abouts (the first stage standard). The bigger issue you
have to deal with using a typical first stage is that the air pressure
is close to equalizing the pressure at 337 feet. If you push the vessel
to it's limit you could end up in a situation whereby you can't blow
ballast because the outside pressure equals or is greater to that being
put out by the first stage.
On 11/23/2013 2:46 PM, Pete Niedermayr wrote:
> I found these 3 way valves that have an off position. I want to go with the Vent/Off/Fill idea I mentions a few months back. I'll have a 1st stage reg on my HP tanks. the valves are rated 600 psi WOG is that high enough ? The K350 spec'ed one are 1000 psi. Any thoughts ?
>
>
> On Sat, 11/23/13, Alec Smyth <alecsmyth at gmail.com> wrote:
>
> Subject: Re: [PSUBS-MAILIST] MBT valve
> To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
> Date: Saturday, November 23, 2013, 9:48 AM
>
> One more thing... I'm not
> sure how easy it would be to get a really accurate seal if
> you make the body from PVC. I always find plastics
> challenging when it comes to machining tolerances. For
> surfacing the sub a tiny valve leak is no problem, in fact
> you wouldn't even notice it. But a tiny leak is a
> nuisance, because the sub will have a tendency to dive
> herself in slow motion when you leave her at the dock for a
> few hours, when she's under tow, etc.
>
> :)
> Alec
>
> On Sat, Nov 23, 2013 at
> 12:35 PM, hank pronk <hanker_20032000 at yahoo.ca>
> wrote:
>
>
> Jon,I have to agree with
> Alec. I would not use an electric motor. If it has to be
> electric, I would also go with solenoid valves. I have
> personally used solenoid valves on my salvage rov and in
> about a million dives we never had a single issue except for
> freezing when the rov surfaced in the winter. Electric
> solenoids are also safe in your case because you have
> multiple mbt's and you should wire them separately.
>
> Hank
>
>
> On Saturday, November 23, 2013 10:10:28 AM,
> Alec Smyth <alecsmyth at gmail.com>
> wrote:
>
> Hi
> Jon,
> Personally if I used a
> remotely operated valve I'd be much more comfortable
> with actuating it pneumatically than electrically, for
> reliability. This is after all the MBT valve, arguably the
> one thing on the sub that has to be the most reliable of
> all. If for some reason it just had to be electric, then
> I'd suggest using an electromagnet instead of a motor.
> The magnet would act against a spring so that the valve was
> of the normally closed type, and you could still surface if
> the electrons got wet.
>
>
> What I don't like about
> the K valves is the way George mounted them. But I'm a
> fan of the approach if you add a proper through-hull for the
> shaft, sealed with O rings instead of RTV like the original.
> If using a large bore valve, I'd add one more detail,
> which is to put round handles on them instead of straight
> ones. That's so that someone getting in or out of the
> sub won't dive it by snagging their clothes on the
> handles.
>
>
>
> Best,
> Alec
>
> On Sat, Nov 23, 2013 at 11:51 AM, Jon
> Wallace <jonw at psubs.org> wrote:
>
>
>
>
> Looking for feedback on this MBT poppet design (see
> attachment). It is very similar to the poppet Vance showed
> us in Islamorada but driven by an independent electric motor
> rather than pneumatic. My goal is to move to an electric
> or pneumatic replacement for the Kittredge MBT ball valve
> thru-hull design for various reasons. First, I don't
> like the valve handles sticking in through the conning
> tower; second, I am adding saddle tanks for additional
> buoyancy which would mean adding at least one more valve;
> third, my saddle tanks are going to be big and I want a
> large diameter valve to provide quick venting.
>
>
>
>
>
> Illustration.
>
> The valve is made out of PVC plumbing material available at
> any good hardware store. The square main body is a 4-inch
> PVC coupling. A series of 1-inch holes drilled into the
> end allow venting when the "plunger" is retracted
> back to the motor side. The "stop" on the closed
> side would have a gasket to provide an air-tight seal.
>
>
>
>
>
> The motor is a cheap electric screwdriver motor such as
> Black & Decker AS6NG. It has plenty of torque,
> reversible, and is low power (2-3vdc). When the body is
> removed the "guts" fit nicely into 1.5 inch PVC
> piping. The rotating socket tip will be waterproofed using
> a home-made "Blue-Globe" type attachment. Oil
> compensation will ensure the housing doesn't fracture at
> depth although theoretically 1.5 inch PVC is pressure safe
> to well beyond the depths I will be diving.
>
>
>
>
>
> The piston will be 1/4 inch thick (6mm) and can be aluminum
> or even 1/4 to 3/8 acrylic. It is attached to the coupling
> nut by a 1/4-20 threaded rod. The coupling nut is
> permanently attached to the rotating socket tip of the
> screwdriver by either epoxy or light welding. As the motor
> and coupling nut turns, the threaded rod is drawn into the
> coupling nut pulling the piston toward the motor and
> allowing the MBT to vent. Reverse the motor and the piston
> is forced back down to the closed position and seals the
> MBT.
>
>
>
>
>
> I have already prototyped the motor and it's PVC housing
> and they fit together very well. Cost of battery operated
> screwdriver is about $10-20 (US). PVC of course, is cheap.
> I am looking at 4-inch material but this design could be
> easily scaled.
>
>
>
>
>
> I see lots of pros; looking for cons and potential issues
> with the design before I fully prototype it. Any of you
> CAD'rs interested in creating a nice 3-D drawing for
> me?
>
>
>
>
>
> Jon
>
>
>
>
>
>
>
>
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